Wheel forces are measured at tire test stands in the laboratory and on mobile test vehicles to test and optimize tires and rims but also wheel suspensions and shock absorbers. Generally, two kinds of test arrangements are used for this purpose. In the first, the force sensors are mounted in the stationary region of the wheels at test stands or test vehicles, in so called measuring hubs, and in the second in the mobile regions of the wheels, for example in the rims of test vehicles. In both arrangements, several sensors are uniformly arranged around the wheel axis in a circle in the corresponding applications. Examples are the measuring hub type 9295 or the measuring wheel type 9296, which both are supplied by Kistler company.
Problems arise with applications for heavy truck wheels since in these cases much higher forces are transmitted. Conventional applications withstand total forces of up to 30 kN in wheel normal direction and up to 20 kN in the other directions. Since said total forces are directed through the load cells, they have to be designed in a corresponding manner. Load cells which are too weak might break during a test run and thus endanger the driver.
In order to be able to measure such high forces, either larger quartz discs or multiple load cells of conventional size have to be used. Often, there is not enough space for larger quartz discs, since the freely available area is limited to the outside by the radius of the rims and to the inside by the large shafts. If a larger number of quartz discs is used, the large number of charge channels which have to be carried by each of the quartz discs will become problematical. On the other hand, the assembly and disassembly of the wheels thus becomes more complicated, since each quartz disc has to be preloaded separately.